Magnetoresistive stack/structure and methods therefor

ABSTRACT

A magnetoresistive device comprises a fixed magnetic region positioned on or over a first electrically conductive region, an intermediate layer positioned on or over the fixed magnetic region, a free magnetic region positioned on or over the intermediate layer, and a metal insertion substance positioned in contact with the free magnetic region, wherein the metal insertion substance includes one or more transition metal elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/530,566, filed Jul. 10, 2017, the disclosure of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to, among other things, embodiments andaspects of magnetoresistive stacks/structures and methods therefor,including methods of use and methods of manufacturing the disclosedmagnetoresistive stacks/structures.

INTRODUCTION

There are many inventions described and illustrated herein, as well asmany aspects and embodiments of those inventions. In one aspect, thepresent disclosure relates to a magnetoresistive stack/structure (forexample, a magnetoresistive memory stack/structure or a magnetoresistivesensor/transducer stack/structure) and methods of manufacturing such astack/structure. In one embodiment of this aspect of the disclosure, thedescribed magnetoresistive stack/structure (for example, a magnetictunnel junction (MTJ) stack/structure) includes an insertion layerhaving a material composition and an associated thickness, disposed on aregion including one or more layers of magnetic or ferromagneticmaterials, that improves the reliability, thermal stability, and/orthermal endurance of the magnetoresistive stack/structure.

For example, the insertion layer may include one or more metals, suchas, e.g., transition metals, including, but not limited to, scandium,titanium, vanadium, chromium, manganese, copper, zinc, yttrium,zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver,cadmium, indium, tin, antimony, lanthanum, cerium, praseodymium,neodymium, samarium, europium, terbium, dysprosium, holmium, erbium,ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium,iridium, platinum, gold, mercury, thallium, lead, and bismuth. Inaddition, the insertion layer may include any metal that does notexhibit ferromagnetic properties when in a pure metal state at roomtemperature. The disclosed insertion layer may have a thickness lessthan or equal to 1 atomic layer for the material of the insertion layer.For example, in embodiments where the insertion layer includes chromium,the insertion layer may have a thickness ranging from approximately 0.2angstrom (Å) to approximately 0.7 Å, from approximately 0.4 Å toapproximately 0.6 Å, greater than approximately 0.2 Å, or less thanapproximately 0.7 Å. In those embodiments where the insertion layerincludes iridium, the insertion layer may have a thickness ofapproximately 0.8 Å or less than approximately 2 Å. Layers with theaforementioned thickness properties may be referred to herein asmonolayers.

In one embodiment, the disclosed insertion layer is implemented in anMTJ-type magnetoresistive stack/structure having a perpendicularmagnetic anisotropy, wherein the MTJ-type structure maintains orincludes improved properties (for example, thermally stable dataretention capabilities (e.g., at relatively higher temperatures),magnetoresistance (MR) and resistance-area product (RA) of thestack/structure) after subsequent or additional processing (for example,annealing processes after deposition/formation of the magnetic region).

Notably, the embodiments described herein may employ any technique nowknown or later developed to manufacture the MTJ stack/structureincluding the formation and/or deposition of the described insertionlayer; all such techniques are intended to fall within the scope of thepresent disclosure. In one embodiment, the described MTJ stack/structuremay be implemented as a magnetoresistive memory stack/structure.

Briefly, a magnetoresistive memory stack/structure, in one embodiment,includes at least one non-magnetic layer (for example, at least onedielectric layer or at least one conductive) disposed between a “fixed”magnetic region/layer and a “free” magnetic region/layer, each includinga plurality of layers of one or more magnetic or ferromagneticmaterials. Information is stored in the magnetoresistive memorystack/structure by switching, programming, and/or controlling thedirection of magnetization vectors in one or more of the magnetic layersof the “free” magnetic region/layer of the stack/structure. Here, thedirection of the magnetization vectors of the “free” magneticregion/layer may be switched and/or programmed (for example, throughspin transfer torque or spin-orbit torque) by application of a writesignal (e.g., one or more current pulses) to or through themagnetoresistive memory stack/structure while, in contrast, themagnetization vectors in the magnetic layers of a “fixed” magneticregion/layer are magnetically fixed (in a predetermined direction).

The magnetoresistive memory stack/structure includes an electricalresistance that depends on the magnetic state of certain regions of thememory stack/structure. That is, when the magnetization vectors of the“free” magnetic region/layer are in a first state or in a firstdirection (for example, which is the same direction as the direction ofthe magnetization vectors of the “fixed” magnetic region/layer), themagnetoresistive memory stack/structure has a first magnetic state,which may correspond to a low electrical resistance state. Conversely,when the magnetization vectors of the “free” magnetic region/layer arein a second state or in a second direction (for example, which is adifferent direction (for example, opposite or opposing) as the directionof the magnetization vectors of the “fixed” magnetic region), themagnetoresistive memory stack/structure has a second magnetic state,which may correspond to a high electrical resistance state. The magneticstate of the magnetoresistive memory stack/structure is determined orread based on the resistance of the stack/structure in response to aread current of a read operation.

As alluded to above, the present disclosure is directed to, among otherthings, a magnetoresistive stack/structure—for example, amagnetoresistive memory stack/structure or a magnetoresistivesensor/transducer stack/structure including an insertion layer having amaterial composition and an associated thickness, disposed on a regionincluding one or more layers of magnetic or ferromagnetic materials,such as, e.g., the “free” magnetic region described above. One, some, orall of the aspects described herein may facilitate an MTJ-typemagnetoresistive stack/structure of the present disclosure to includeand/or maintain improved characteristics or properties (for example,high temperature data retention capabilities, magnetoresistance (MR) andresistance-area product (RA) of the stack/structure), even after beingexposed to elevated temperatures (e.g., approximately 170° C. toapproximately 260° C.) during, e.g., reflow soldering process orimplementation in an automotive applications. Indeed, a stack/structureincluding such an insertion layer may exhibit improved reliability,thermal stability and/or thermal endurance of the magnetoresistivestack/structure, for example, a magnetoresistive memory stack/structure.

Embodiments of the present disclosure also are directed tomagnetoresistive integrated circuit devices (for example, a spin-torqueMRAM) having one or more magnetoresistive stacks/structures (forexample, a plurality of MTJ stacks/structures of a MTJ-basedsensor/transducer device and/or MTJ-based memory device). Certainexemplary embodiments are described below.

In some embodiments, a magnetoresistive device is disclosed. The devicemay include a fixed magnetic region, a free magnetic region, and anintermediate layer disposed in between the fixed magnetic region and thefree magnetic region. The device may also include one or more insertionmaterial or substance disposed on or above the free magnetic region,wherein the insertion substance may include one or more transitionmetals, including, but not limited to, chromium (Cr), iridium (Ir), oralloys thereof. The insertion substance may be provided (e.g., viadeposition) in a volume or quantity that is intended to create athickness that is less than or equal to one monolayer thick. In actualpractice, however, the provided volume or quantity may have a differentthickness. Also, the substance may be provided in a non-uniform manner,such that, the substance does not provide a constant layer coating orcovering on or above the free magnetic region. Indeed, in some areas,the lack of uniformity in providing the substance may leave portions ofthe free magnetic region devoid of the substance.

Different embodiments of the disclosed magnetoresistive devices may haveone or more of the following aspects: the intermediate layer may includea dielectric material; the intermediate layer may include a conductivematerial; the fixed magnetic region may include a multilayer syntheticantiferromagnetic structure; the device may further include a cappinglayer disposed on or above the insertion elements, wherein the insertionelements is positioned between the capping layer and the free layer; thedevice may further include a second fixed region disposed on or abovethe insertion elements, wherein the insertion elements is positionedbetween the second fixed region and the free region.

In some embodiments, a method of manufacturing a magnetoresistive stackis disclosed. The method may include depositing a fixed magnetic regionon an electrically conductive material; depositing a free magneticregion; depositing one or more intermediate layers in between the fixedmagnetic region and the free magnetic region; and depositing one or moreinsertion elements on or above the free magnetic region, wherein theinsertion elements include one of chromium and iridium and is less thanor equal to one monolayer thick.

Different embodiments of the disclosed method may have one or more ofthe following aspects: further comprise depositing a second intermediatelayer on or above the insertion elements; depositing a second fixedregion on or above the second intermediate layer; the secondintermediate layer may include a dielectric material; the intermediatelayer may include a conductive material; the fixed magnetic region mayinclude a multilayer synthetic antiferromagnetic structure.

Notably, although certain exemplary embodiments are described and/orillustrated herein in the context of MTJ stacks/structures, the presentinventions may be implemented in giant magnetoresistive (GMR)stacks/structures where a conductor (e.g., copper) is disposed betweentwo ferromagnetic regions/layers/materials. Indeed, the presentinventions may be employed in connection with other types ofmagnetoresistive stacks/structures wherein such stacks/structuresinclude a fixed magnetic region. For the sake of brevity, thediscussions and illustrations will not be repeated specifically in thecontext of GMR or other magnetoresistive stacks/structures—but suchdiscussions and illustrations are to be interpreted as being entirelyapplicable to GMR and other stacks/structures.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure may be implemented in connectionwith aspects illustrated in the attached drawings. These drawings showdifferent aspects of the present inventions and, where appropriate,reference numerals illustrating like structures, components, materialsand/or elements in different figures are labeled similarly. It isunderstood that various combinations of the structures, components,and/or elements, other than those specifically shown, are contemplatedand are within the scope of the presently disclosed embodiments.

For simplicity and clarity of illustration, the figures depict thegeneral structure and/or manner of construction of the variousembodiments. For ease of illustration, the figures depict the differentlayers/regions of the illustrated stacks as having a uniform thicknessand well-defined boundaries with straight edges. However, a personskilled in the art would recognize that, in reality, the differentlayers typically have a non-uniform thickness. And, at the interfacebetween adjacent layers, the materials of these layers alloy together,or migrate into one or the other material, making their boundaries illdefined. Descriptions and details of well-known features (e.g.,interconnects, etc.) and techniques may be omitted to avoid obscuringother features. Elements in the figures are not necessarily drawn toscale. The dimensions of some features may be exaggerated relative toother features to improve understanding of the exemplary embodiments.Cross-sectional views are simplifications provided to help illustratethe relative positioning of various regions/layers and describe variousprocessing steps. One skilled in the art would appreciate that thecross-sectional views are not drawn to scale and should not be viewed asrepresenting proportional relationships between differentregions/layers. Moreover, while certain regions/layers and features areillustrated with straight 90-degree edges, in actuality or practice suchregions/layers may be more “rounded” and gradually sloping.

Further, one skilled in the art would understand that, although multiplelayers with distinct interfaces are illustrated in the figures, in somecases, over time and/or exposure to high temperatures, materials of someof the layers may migrate into or interact with materials of otherlayers to present a more diffuse interface between these layers. Itshould be noted that, even if it is not specifically mentioned, aspectsdescribed with reference to one embodiment may also be applicable to,and may be used with, other embodiments.

Moreover, there are many embodiments described and illustrated herein.The present disclosure is neither limited to any single aspect norembodiment thereof, nor to any combinations and/or permutations of suchaspects and/or embodiments. Moreover, each aspect of the presentdisclosure, and/or embodiments thereof, may be employed alone or incombination with one or more of the other aspects of the presentdisclosure and/or embodiments thereof. For the sake of brevity, certainpermutations and combinations are not discussed and/or illustratedseparately herein. Notably, an embodiment or implementation describedherein as “exemplary” is not to be construed as preferred oradvantageous, for example, over other embodiments or implementations;rather, it is intended reflect or indicate the embodiment(s) is/are“example” embodiment(s). Further, even though the figures and thiswritten disclosure appear to describe the disclose magnetoresistivestack/structures in a particular order of construction (e.g., frombottom to top), it is understood that the depicted magnetoresistivestack/structures may have the opposite order (e.g., from top to bottom).For example, a “fixed” magnetic region/layer may be formed on or above a“free” magnetic region or layer, which in turn may be formed on or abovean insertion layer of the present disclosure.

FIG. 1A illustrates a cross-sectional view of layers of an exemplaryMTJ-type magnetoresistive stack/structure (for example, an in-plane orout-of-plane magnetic anisotropy magnetoresistive stack/structure (e.g.,a perpendicular magnetic anisotropy magnetoresistive stack/structure))including an intermediate layer (e.g., a dielectric layer), disposedbetween a “free” magnetic region (or layer) and a “fixed” magneticregion (or layer) wherein, in some exemplary embodiments, the “fixed”magnetic layer may be disposed between an electrode and an intermediatelayer (which may be a tunnel barrier in the completed structure),according to at least certain aspects of certain embodiments describedherein. In one or more exemplary embodiments, the MTJ-typemagnetoresistive stack/structure is disposed between and in physicalcontact with one or more electrically conductive regions (e.g.,electrodes, vias, lines) including (for example, in the context ofelectrodes or vias, tantalum, or an alloy thereof (such as atantalum-nitride alloy), or a composite thereof (such as a tantalum (Ta)and tantalum-nitride (TaN) alloy composite)); notably, the “free”magnetic layer and the “fixed” magnetic layer may each include aplurality of layers of magnetic or ferromagnetic material(s) (forexample, nickel (Ni), iron (Fe), cobalt (Co), palladium (Pd), platinum(Pt), magnesium (Mg), manganese (Mn), chromium (Cr), and alloys thereof)as well as one or more synthetic antiferromagnetic structures (SAF) orsynthetic ferromagnetic structures (SyF), wherein one or more layers ofmagnetic materials layers may also include one or more non-magneticmaterials layers (for example, ruthenium (Ru), copper (Cu), aluminum(Al), tantalum (Ta), titanium (Ti), niobium (Nb), vanadium (V),zirconium (Zr), iridium (Ir), and one or more alloys thereof, and incertain embodiments, tungsten (W) and molybdenum (Mo); moreover, thedielectric layers may be, for example, one or more layers of, forexample, aluminum oxide (Al₂O₃), magnesium oxide (MgO), other metalsoxides, or combinations thereof;

FIG. 1B illustrates another exemplary magnetoresistive stack/structureincluding an SOT switching line disposed near or adjacent to the “free”magnetic region;

FIG. 2 illustrates a cross-sectional view of exemplary layers that maybe included in one exemplary “fixed” magnetic region/layer of theexemplary MTJ-type magnetoresistive stacks/structures depicted in FIGS.1A-1B;

FIG. 3 illustrates a cross-sectional view of exemplary layers that maybe included in another exemplary “fixed” magnetic region/layer of theexemplary MTJ-type magnetoresistive stacks/structures depicted in FIGS.1A-1B, wherein the electrode may include a seed layer or region disposedat its interface with the “fixed” magnetic region/layer;

FIG. 4 illustrates a cross-sectional view of other exemplary layers(e.g., a pinning layer and a pinned layer) that may be included from thebottom electrode to the intermediate layer of the MTJ-typemagnetoresistive stacks/structures depicted in FIGS. 1A-1B;

FIG. 5A illustrates a cross-sectional view of exemplary layers that maybe included in one exemplary “free” magnetic region/layer of theexemplary MTJ-type magnetoresistive stacks/structures depicted in FIGS.1A-1B, wherein an insertion substance may be disposed on or above the“free” magnetic region/layer, and wherein the “free” magneticregion/layer may be disposed on or above an intermediate layer, such asa dielectric layer (which in some embodiments may act as a tunnelbarrier);

FIG. 5B illustrates a top-down view of exemplary layers that may beincluded in the exemplary MTJ-type magnetoresistive stacks/structuresdepicted in FIGS. 1A-1B;

FIG. 6A illustrates a cross-sectional view of exemplary layers that maybe included in another exemplary “free” magnetic region of the exemplaryMTJ-type magnetoresistive stacks/structures depicted in FIGS. 1A-1B,wherein an insertion layer may be provided in the “free” magneticregion/layer and an insertion substance may be disposed on or above the“free” magnetic region;

FIG. 6B illustrates a cross-sectional view of exemplary layers that maybe included in another exemplary “free” magnetic region of the exemplaryMTJ-type magnetoresistive stacks/structures depicted in FIGS. 1A-1B,wherein an insertion layer may be provided in the “free” magneticregion/layer and an insertion substance may be disposed on or above the“free” magnetic region;

FIG. 7 illustrates a cross-sectional view of exemplary layers of anexemplary MTJ-type magnetoresistive stack/structure of the currentdisclosure;

FIG. 8 illustrates a cross-sectional view of exemplary layers of anexemplary double spin filter MTJ-type magnetoresistive stack/structureof the current disclosure;

FIG. 9 is a schematic diagram of an exemplary magnetoresistive memorystack/structure electrically connected to an access transistor in amagnetoresistive memory cell configuration;

FIGS. 10A-10B are schematic block diagrams of integrated circuitsincluding a discrete memory device and an embedded memory device, eachincluding MRAM (which, in one embodiment is representative of one ormore arrays of MRAM having a plurality of magnetoresistive memorystacks/structures, according to aspects of certain embodiments of thepresent disclosure; and

FIGS. 11-12 are simplified exemplary manufacturing flows for theformation (e.g., via deposition) of layers of the exemplary MTJ-typemagnetoresistive stack/structures described herein, according to atleast certain aspects of certain embodiments of the present disclosure,wherein the various layers and/or regions are sequentially deposited,grown, sputtered, evaporated, and/or provided (used herein collectivelyas “deposited” or other verb tense (e.g., “deposit” or “depositing”)) toprovide the material stack that, after further processing, is anMTJ-type magnetoresistive stack/structure (having, for example, aperpendicular magnetic anisotropy).

Again, there are many embodiments described and illustrated herein. Thepresent disclosure is neither limited to any single aspect norembodiment thereof, nor to any combinations and/or permutations of suchaspects and/or embodiments. Each of the aspects of the presentdisclosure, and/or embodiments thereof, may be employed alone or incombination with one or more of the other aspects of the presentdisclosure and/or embodiments thereof. For the sake of brevity, many ofthose combinations and permutations are not discussed separately herein.

DETAILED DESCRIPTION

It should be noted that all numeric values disclosed herein (includingall disclosed thickness values, limits, and ranges) may have a variationof ±10% (unless a different variation is specified) from the disclosednumeric value. For example, a layer disclosed as being “t” units thickcan vary in thickness from (t−0.1t) to (t+0.1t) units. Further, allrelative terms such as “about,” “substantially,” “approximately,” etc.are used to indicate a possible variation of ±10% (unless notedotherwise or another variation is specified). Moreover, in the claims,values, limits, and/or ranges of the thickness and atomic compositionof, for example, the described layers/regions, means the value, limit,and/or range ±10%.

It should be noted that the description set forth herein is merelyillustrative in nature and is not intended to limit the embodiments ofthe subject matter, or the application and uses of such embodiments. Anyimplementation described herein as exemplary is not to be construed aspreferred or advantageous over other implementations. Rather, the term“exemplary” is used in the sense of example or “illustrative,” ratherthan “ideal.” The terms “comprise,” “include,” “have,” “with,” and anyvariations thereof are used synonymously to denote or describe anon-exclusive inclusion. As such, a device or a method that uses suchterms does not include only those elements or steps, but may includeother elements and steps not expressly listed or inherent to such deviceand method. Further, the terms “first,” “second,” and the like, hereindo not denote any order, quantity, or importance, but rather are used todistinguish one element from another. Similarly, terms of relativeorientation, such as “top,” “bottom,” etc. are used with reference tothe orientation of the structure illustrated in the figures beingdescribed. Moreover, the terms “a” and “an” herein do not denote alimitation of quantity, but rather denote the presence of at least oneof the referenced item.

In this disclosure, the term “layer” is used generally to refer to oneor more layers. That is, a layer (as used herein) may include a singlelayer (or coating) of material or multiple layers of materials stackedone on top of another to form a multi-layer system. Further, although inthe description below, the different layers in the disclosedstack/structure are referred to by specific names (capping layer,reference layer, transition layer, etc.), this is only for ease ofdescription and not intended as a functional description of the layer.Moreover, although the description below and the figures appear todepict a certain orientation of the layers relative to each other, thoseof ordinary skill in the art will understand that such descriptions anddepictions are only exemplary. For example, though the “free” magneticlayer or region is depicted as being “above” an intermediate layer, insome aspects the entire stack may be flipped such that the intermediatelayer is “above” the “free” magnetic layer or region.

As alluded to above, in one exemplary aspect, the magnetoresistivestack/structure of the present disclosure may be implemented as aspin-torque magnetoresistive random access memory (“MRAM”) element(“memory element”). In such aspects, the stack/structure may include anintermediate layer positioned (or sandwiched) between two ferromagneticregions/layers to form a magnetic tunnel junction (MTJ) device or anMTJ-type device. The intermediate layer may be a tunnel barrier andinclude an insulating material, such as, e.g., a dielectric material. Inother embodiments, the intermediate layer may be a conductive material,e.g., copper, gold, or alloys thereof. In these other embodiments, wherethe magnetoresistive stack/structure includes a conductive material inbetween two ferromagnetic regions/layers, the magnetoresistivestack/structure may form a GMR or GMR-type device.

Of the two ferromagnetic regions disposed on either side of theintermediate layer, one ferromagnetic region/layer may be a magnetically“fixed” or pinned region, and the other ferromagnetic region/layer maybe a magnetically “free” layer. As alluded to above, the term “free” isintended to refer to ferromagnetic regions having a magnetic moment thatmay shift or move significantly in response to applied magnetic fieldsor spin-polarized currents used to switch the magnetic moment vector. Onthe other hand, the words “fixed” and “pinned” are used to refer toferromagnetic regions having a magnetic moment vector that does not movesubstantially in response to applied magnetic fields, spin-transfertorque, torque from spin-polarized currents, or current-inducedspin-orbit torque originating from the strong spin-orbit coupling inheavy metals and their interfaces (e.g., an SOT switching line). As isknown in the art, an electrical resistance of the describedmagnetoresistive stack/structure may change based on whether themagnetization direction (e.g., the direction of the magnetic moment) ofthe “free” region is in a parallel alignment or in an antiparallelalignment with the magnetization direction (e.g., the direction of themagnetic moment) of the “fixed” region. Typically, if the two regionshave the same magnetization alignment, the resulting low resistance isconsidered as a digital “0,” while if the alignment is antiparallel theresulting higher resistance is considered to be a digital “1.” A memorydevice (such as an MRAM) may include multiple such magnetoresistivestacks/structures, which may be referred to as memory cells or elements,arranged in an array of columns and rows. By measuring the currentthrough each cell, the resistance of each cell, and thus the data storedin the memory array can be read.

Switching the magnetization direction of the “free” region of amagnetoresistive stack/structure may be accomplished by driving atunneling current pulse through the magnetoresistive stack/structure.The polarity of the current pulse determines the final magnetizationstate (i.e., parallel or antiparallel) of the “free” region. The meancurrent required to switch the magnetic state of the “free” region maybe referred to as the critical current (Ic). The critical current isindicative of the current required to “write” data in (or the writecurrent of) a magnetoresistive memory cell. Reducing the required writecurrent(s) is desirable so that, among other things, a smaller accesstransistor can be used for each memory cell and a higher density, lowercost memory can be produced. Another way of switching the magnetizationdirection of the “free” region may be accomplished by current-inducedspin-orbit torque (SOT) magnetization switching.

Magnetoresistance ratio (MR) is the ratio of the change in resistance ofa magnetoresistive stack/structure between its high and low resistancestates (MR=(R_(H)−R_(L))/R_(L), where R_(L) and R_(H) are the resistanceof the magnetoresistive stack/structure in the low and high resistancestates, respectively). MR is indicative of the strength of the signalwhen a memory element is “read.” For an MTJ-type magnetoresistivestack/structure with a strong read signal, a larger MR (e.g., a largerdifference between the individual resistances R_(H) and R_(L)) isdesirable. When the intermediate layer of magnetoresistivestack/structure is a tunnel barrier made of a dielectric material, theresistance may be measured by the resistance-area product (RA).

For the sake of brevity, conventional techniques related tosemiconductor processing may not be described in detail herein. Theexemplary embodiments may be fabricated using known lithographicprocesses. The fabrication of integrated circuits, microelectronicdevices, micro electro mechanical devices, microfluidic devices, andphotonic devices involves the creation of several layers of materialsthat interact in some fashion. One or more of these layers may bepatterned so various regions of the layer have different electrical orother characteristics, which may be interconnected within the layer orto other layers to create electrical components and circuits. Theseregions may be created by selectively introducing or removing variousmaterials. The patterns that define such regions are often created bylithographic processes. For example, a layer of photoresist is appliedonto a layer overlying a wafer substrate. A photo mask (containing clearand opaque areas) is used to selectively expose the photoresist by aform of radiation, such as ultraviolet light, electrons, or x-rays.Either the photoresist exposed to the radiation, or not exposed to theradiation, is removed by the application of a developer. An etch maythen be performed whereby the layer not protected by the remainingresist is patterned. Alternatively, an additive process can be used inwhich a structure is built up using the photoresist as a template.

As noted above, in one aspect, the described embodiments relate to,among other things, methods of manufacturing a magnetoresistivestack/structure having one or more electrically conductive regions(e.g., electrodes, vias, or conductors) on either side of a magneticmaterial stack. As described in further detail below, the magneticmaterial stack may include many different layers of material, where someof the layers include magnetic materials, whereas others do not. In oneembodiment, the methods of manufacturing include sequentiallydepositing, growing, sputtering, evaporating, and/or providing (as notedabove, herein collectively “depositing” or other verb tense (e.g.,“deposit” or “deposited”)) layers and regions which, after furtherprocessing (for example, etching) those layers form a magnetoresistivestack/structure.

The magnetoresistive stacks/structures of the present inventions may beformed between a top electrode/via/line (e.g., electrode 90) and abottom electrode/via/line (e.g., electrode 10) and, which permit accessto the stack/structure by allowing for connectivity (for example,electrical) to circuitry and other elements of the magnetoresistivedevice. Between the electrodes/vias/lines are layers and/or regions,including at least one “fixed” magnetic region (which includes, amongother things, a plurality of ferromagnetic layers), a seed region, atleast one “free” magnetic region (which includes, among other things, aplurality of ferromagnetic layers), and one or more intermediate layers(e.g., one or more dielectric layers)—including at least oneintermediate layer, disposed between the “fixed” magnetic region and the“free” magnetic region. The intermediate layer may function as a tunnelbarrier layer between “fixed” magnetic region and “free” magneticregion. As explained in greater detail below, the magnetoresistivestacks/structures of the present inventions also include at least oneinsertion layer (e.g., formed of a metal, including a transition metal,such as, e.g., chromium (Cr) or iridium (Ir)) between the top electrode90 and the “free” magnetic region 60.

FIG. 1A is a cross-sectional view of regions (or layers) of an exemplaryMTJ-type magnetoresistive stack/structure 100 (for example, an in-planeor out-of-plane magnetic anisotropy magnetoresistive stack/structure(e.g., a perpendicular magnetic anisotropy magnetoresistivestack/structure)). It will be recognized that, for clarity, severalother commonly-used regions (or layers) (e.g., various protective caplayers, seed layers, underlying substrate, etc.) have not beenillustrated in FIG. 1A (and in subsequent figures). As illustrated inFIG. 1A, magnetoresistive stack/structure 100 may include multipleregions (or layers) arranged one over the other to form a stack oflayers between a first electrode 10 and a second electrode 90. As shownin FIG. 1A, first electrode 10 may be a “bottom” electrode, and secondelectrode 90 may be a “top” electrode. However, those of ordinary skillin the art will recognize that the relative order of the various regions(or layers) of magnetoresistive stack/structure 100 may be reversed.Further, in some embodiments, the top electrode 90 (and/or the bottomelectrode 10) may be eliminated, and the bit line may be formed on topof the stack. The bottom electrode 10 and top electrode 90 may comprisean electrically conductive material, and may be part of (or be inphysical contact with) electrically conductive interconnects (e.g.,vias, traces, lines, etc.) of magnetoresistive stack/structure 100(e.g., as shown in FIG. 10). Although any electrically conductivematerial may be used for bottom electrode 10 and top electrode 90, insome embodiments, a metal such as tantalum (Ta), titanium (Ti), tungsten(W), or a composite or alloy of these elements (e.g., tantalum-nitride(TaN) alloy) may be used.

With continuing reference to FIG. 1A, “fixed” region 20 may be formed onor above bottom electrode 10. Although not illustrated in FIG. 1A, insome embodiments, bottom electrode 10 may be formed on a planar surfaceof a semiconductor substrate (e.g., silicon substrate, etc.). “fixed”region 20 may serve as a “fixed” magnetic region of magnetoresistivestack/structure 100. That is, a magnetic moment vector in the “fixed”region 20 does not move significantly in response to applied magneticfields (e.g., an external field) or applied currents used to switch themagnetic moment vector of “free” region 60, as explained above. Whilethe “fixed” region 20 of FIG. 1A is shown as a single layer, “fixed”region 20 may include several layers of a magnetic or a ferromagneticmaterial. In addition, “fixed” region 20 may include additional layers,including, but not limited to, an antiferromagnetic coupling layer, areference layer, and/or a transition layer, as described below ingreater detail, e.g., in connection with FIG. 3.

In some embodiments, the layers of “fixed” region 20 may include alloysthat include cobalt (Co) and iron (Fe) (preferably cobalt (Co), iron(Fe), and boron (B)). In some embodiments, the composition of materials(e.g., cobalt (Co), iron (Fe), and boron (B)) in the “fixed” region 20may be selected to achieve good temperature compensation. In someembodiments, these layers may also include, for example, alloys orengineered materials with one or more of palladium (Pd), platinum (Pt),magnesium (Mg), manganese (Mn), and chromium (Cr). Additionally oralternatively, in some embodiments, the “fixed” region 20 may includeone or more synthetic antiferromagnetic structures (SAF) or syntheticferromagnetic structures (SyF). Since SAFs and SyFs are known to thoseskilled in the art, additional description is omitted for sake ofbrevity.

In some embodiments, “fixed” region 20 also may include one or morenon-magnetic material layers. For example, ruthenium (Ru), copper (Cu),aluminum (Al), tantalum (Ta), titanium (Ti), niobium (Nb), vanadium (V),zirconium (Zr), iridium (Ir), one or more alloys of these elements, andin certain embodiments, tungsten (W) and molybdenum (Mo). In someembodiments, “fixed” region 20 may include a multi-layer structure ofcobalt (Co) and platinum (Pt) or cobalt (Co) and nickel (Ni) (with orwithout other alloying elements). For example, in embodiments where“fixed” region 20 is a multi-layer structure of cobalt (Co) and platinum(Pt), “fixed” region 20 may include a cobalt (Co) layer (e.g., formed onor above a surface of electrode 10) followed by a platinum (Pt) layerformed on or above a surface of the cobalt (“Co”) layer. In general,“fixed” region 20 may have any thickness. In some embodiments, the“fixed” region 20 may have a thickness in the range of betweenapproximately 8 Å and approximately 300 Å, between approximately 15 Åand approximately 110 Å, greater than or equal to 8 Å, greater than orequal to 15 Å, less than or equal to 300 Å, or less than or equal to 110Å. “fixed” region 20 may be deposited or formed using any technique nowknown or later developed; all of which are intended to fall within thescope of the present disclosure.

In some embodiments, such as the one shown in FIG. 1B, magnetoresistivestack/structure 100 may further include an SOT switching line 70disposed next to, adjacent to, and/or in contact with “free” region 60.The SOT switching line 70 may include one or more heavy metals. In someembodiments, the SOT switching line 70 may include, for example,platinum (Pt), alloys of bismuth (Bi) including Bi_(x)Se_(1-x),(Bi_(0.5)Sb_(0.5))₂Te₃, and Bi_(x)Sb_(1-x), beta-tungsten (β-W),beta-tantalum (β-Ta), or one or more alloys including tantalum (Ta),niobium (Nb), hafnium (Hf), zirconium (Zr), and/or titanium (Ti). Theelectrons flowing through the SOT switching line produce a spin currentdue to the strong spin-orbit coupling in the constituent metals andtheir interfaces. This spin current transfers its angular momentum tothe adjacent “free” region 60, and thus switches the magnetizationdirection of the “free” region.

Turning now to FIG. 2, an exemplary embodiment of “fixed” region 20having a plurality of layers is shown. It should be noted that, for thesake of clarity, only certain layers that comprise the “fixed” region20, and only certain exemplary regions/layers on either side of the“fixed” region 20 (e.g., electrode 10 and intermediate layer 50) areillustrated in FIG. 2. Those of ordinary skill in the art will readilyrecognize that one or more additional layers, interface areas, and/orregions may be included within “fixed” region 20 and/or may be disposedbetween the layers of “fixed” region 20 and the depicted exemplaryregions on either side of “fixed” region 20.

In one example, “fixed” region 20 may be a fixed, unpinned syntheticantiferromagnetic (SAF) region disposed on or above electrode 10. Thefixed, unpinned synthetic antiferromagnetic (SAF) region may include atleast two magnetic regions or layers 22, 32 (e.g., ferromagnetic layer 1and ferromagnetic layer 2 in FIG. 2) separated by a coupling layer 30.One or more of magnetic regions or layers 22, 32 may include one or moreof the ferromagnetic elements nickel (Ni), iron (Fe), and cobalt (Co),including alloys or engineered materials with one or more of theelements palladium (Pd), platinum (Pt), chromium (Cr), and alloysthereof. The coupling layer 30 may be an antiferromagnetic (AF) couplinglayer including, e.g., non-ferromagnetic materials such iridium (Ir),ruthenium (Ru), or rhodium (Rh).

In some aspects at least one of the magnetic regions or layers 22, 32may include a magnetic multi-layer structure including a plurality oflayers (i) of a first ferromagnetic material (e.g., cobalt) and (ii) asecond ferromagnetic material (e.g., nickel) or a paramagnetic material(e.g., platinum). For example, as shown in FIG. 3, magnetic region orlayer 32 may include a multi-layer structure, as described in greaterdetail below.

In one embodiment, the interfacial layers of a multi-layer magneticstructure (e.g., layer 32 in FIG. 3) of the fixed, unpinned SAF region(for example, depending on the location of the multi-layer structurewithin the fixed unpinned SAF region—layers that are in contact orinterface with bottom electrode 10, seed region 12, the AF couplinglayer 30, transition layer 34, and/or the intermediate layer 50) includea layer of ferromagnetic material having a thickness which is greaterthan the thicknesses of one or more (or all) of the internal layers ofthe multi-layer magnetic region (i.e., layers of (i) of a firstferromagnetic material (e.g., cobalt) and (ii) a second ferromagneticmaterial (e.g., nickel (Ni)) or paramagnetic material (e.g., platinum).For example, in one embodiment, an interfacial layer of ferromagneticmaterial may include a thickness that is, for example, 15-30%, 20-40%,or 25-50% greater than the thickness of the internal layers of themulti-layer magnetic structure. Indeed, where the multi-layer magneticstructure includes layers of cobalt and layers of platinum, in oneembodiment, interfacial layers of cobalt include a thickness (forexample, a thickness which is greater than approximately 4 Å and lessthan approximately 8 Å), which is greater than the thickness of theinternal layers, which may be alternating layers of platinum and cobalt.In one exemplary embodiment, the internal layers of platinum and cobaltinclude a thickness greater than approximately 2 Å and less thanapproximately 6 Å and preferably greater than approximately 2.5 and lessthan approximately 4.5 Å and more preferably approximately 3 Å.

In some embodiments, the multi-layer magnetic structure includes layersof nickel (Ni) and layers of cobalt (Co), and interfacial layersincluding nickel (Ni) may include a thickness (for example, greater thanapproximately 4 Å and less than approximately 8 Å), which is greaterthan a thickness of any or all of the internal layers combined. In oneexemplary embodiment, the internal layers of cobalt and nickel include athickness greater than 2 Å and less than 6 Å and preferably greater than2.5 and less than 4.5 Å and more preferably 3 Å.

Notably, in one embodiment, only one of the interfacial layers of one orboth multi-layer magnetic regions (e.g., layers 22, 32) of the fixed,unpinned SAF region includes a thickness which is greater than thethicknesses of one or more (or all) of the associated internal layers ofthe multi-layer magnetic structure of the fixed, unpinned SAF region.

In some embodiments, e.g., as described in greater detail below andshown in FIG. 3, electrode 10 of the magnetoresistive stack/structure100 may include a seed region 12. In some embodiments, the top surfaceof electrode 10 itself may act as the seed region 12, e.g., when otherseed region 12 is not provided. After deposition/formation of seedregion 12, the overlying region or layer (e.g., “fixed” magnetic region20) may be formed (e.g., deposited) on seed region 12 of electrode 10.The seed region layer 12 may assist in the formation of the “fixed”magnetic region or layer 20. As alluded to above, seed region 12 may beomitted if the overlying region or layer does not require assistance inbeing formed on electrode 10. The “fixed” magnetic region 20, asdiscussed above, may include a multi-layer, fixed unpinned SAF includinga plurality of layers of one or more magnetic or ferromagnetic materials22, 32 (for example, a multi-layer structure of (i) cobalt and platinumor (ii) cobalt and nickel separated by an AF coupling layer 30 (forexample, an AF coupling layer 30 including non-ferromagnetic materialsuch as ruthenium having a thickness of, for example, 4 Å (+/−1 Å)).

As alluded to above, some aspects of the present disclosure may includea seed region 12 disposed between bottom electrode 10 and “fixed” region20. In practice, the seed region 12 may facilitate the formation of the“fixed” region 20 on the electrode 10. In embodiments where electrode 10provides the desired growth characteristics for the subsequent layers,the seed region 12 may be omitted. Though seed region 12 is depicted inFIG. 3 as a single layer, those of ordinary skill in the art willunderstand that in some embodiments, seed region 12 also may include amulti-layer structure. The seed region 12 may include one or more ofnickel, chromium, cobalt, iron, and alloys thereof (for example, analloy including nickel and chromium). Further, seed region 12 may have athickness which is greater than or equal to approximately 30 Å, greaterthan or equal to approximately 40 Å, greater than or equal toapproximately 50 Å, or preferably greater than or equal to approximately60 Å, more preferably greater than or equal to approximately 40 Å, orgreater than approximately 50 Å and less than or equal to approximately100 Å, approximately 40 Å to approximately 60 Å, or even more preferablygreater than or equal to approximately 60 Å and less than or equal toapproximately 100 Å, or most preferably approximately 60 Å (+/−10%). Asdepicted in FIG. 3, the seed region 12 may be disposed between and inphysical contact with an electrically conductive metal material of anelectrode/via/line (e.g., electrode 10) and “fixed” magnetic region 20.

In addition, “fixed” magnetic region 20 may include a transition layer34 and/or a reference layer 36 disposed between magnetic layer 32 andintermediate layer 50 (e.g., a dielectric layer which may form a tunnelbarrier). The transition layer 34 and/or reference layer 36 may includeone or more layers of material that, among other things,facilitate/improve growth of the intermediate layer 50 duringfabrication. In one embodiment, reference layer 36 includes one or moreor all of cobalt (Co), iron (Fe), and boron (B) (for example, in analloy—such as an amorphous alloy (e.g., CoFeB or CoFeBTa or CoFeTa)). Inone or more embodiments, transition layer 34 may include anon-ferromagnetic transition metal such as tantalum (Ta), titanium (Ti),tungsten (W), ruthenium (Ru), niobium (Nb), zirconium (Zr), and/ormolybdenum (Mo).

In some embodiments, reference layer 36 also may include a multi-layerstructure. For example, reference layer 36 may include a layer of iron(Fe) (for example, deposited as pure or substantially pure iron) and alayer of cobalt (Co), iron (Fe), and boron (B) (for example, depositedas an alloy), wherein, after further/final processing (e.g., afterannealing), the layer of iron (Fe) at the interface may form acontinuous atomic layer or may mix with the underlying ferromagneticalloy in the final annealed structure, resulting in a high-ironinterface region within reference layer 36 which layer is adjacent tothe intermediate layer 50. For example, the high-iron interface regionmay have an iron (Fe) content greater than or equal to 90 atomic percent(at. %), greater than or equal to 95 at. %, greater than or equal to 99at. %, or greater than or equal to 99.9 at. %. Notably, the referencelayer 34 and/or transition layer 36 may be implemented/employed in anyof the embodiments described herein.

In some embodiments, transition layer 34 may be formed by depositing (orby another process) one or more non-ferromagnetic layers that may alloywith one or more of the neighboring ferromagnetic layers (e.g., layer32), for example, during or in conjunction with one or more subsequentannealing processes to thereby form transition layer 34. In someembodiments, an alloy material may be directly deposited as thetransition layer 34 and/or reference layer 36. In general, transitionlayer 34 and the reference layer 36 may have any thickness. In someembodiments, transition layer 34 has a thickness of approximately 1-8 Å,preferably approximately 1.5-5 Å, and more preferably approximately2.5-3.5 Å. In some embodiments, a reference layer 36 may have athickness of approximately 6-13 Å, preferably approximately 8-12 Å, andmore preferably approximately 9-9.5 Å. In some embodiments where analloy material is directly deposited as the transition layer 34, thethickness of transition layer 34 may be approximately 8 Å. In someembodiments, transition layer 34 and/or reference layer 36 may have asub-atomic thickness. It should be noted that the exemplary thicknessvalues discussed above are expected values of layer thicknessesimmediately after deposition. As a person skilled in the art wouldrecognize, in some cases, after deposition (over time and/or afterexposure to high temperatures, etc.), the material of the depositedlayer may migrate into (diffuse, etc.) adjoining layers (e.g.,underlying layer, etc.) to form an alloy or an adjoining layer with aregion having a higher concentration of the deposited material. In suchembodiments, although the transition and reference layers 34, 36 mayappear as distinct layers immediately after formation of these layers,after subsequent processing operations (e.g., annealing), these layersmay mix or alloy together to form a single alloyed layer with (orseparate from) the “fixed” region 20. Thus, in some cases, it may bedifficult to distinguish layers 34 and 36 as being separate from the“fixed” region 20 in a finished magnetoresistive stack/structure 100 ofthe present disclosure. Instead, a region at the interface of the“fixed” region 20 and its overlying layer (e.g., intermediate layer 50in FIG. 3) may have a greater concentration of the material(s) thatforms the transition layer 34 and/or the reference layer 36.

The reference layer 36 and/or transition layer 34 may be deposited usingany technique now known or later developed; all of which are intended tofall within the scope of the present inventions. However, it may beadvantageous to deposit one or both of the reference layer 36 andtransition layer 34 of the fixed magnetic region using a “heavy” inertgas (for example, xenon (Xe), argon (Ar), and/or krypton (Kr)). In oneembodiment, the reference layer 36 and/or transition layer 34 may bedeposited using the “heavy” sputtering inert gas. In addition thereto,the reference layer 36 and/or transition layer 34 also may be depositedat room temperature (for example, 15-40° C., and more preferably 20-30°C., and most preferably 25° C. (+/−10%)) or an elevated temperature(e.g., 40-60° C.).

Moreover, it may be advantageous to deposit one or more (or all) of themagnetic layers of the “fixed” region 20 using a “heavy” inert gas (forexample, xenon (Xe)), for example, at room temperature (e.g., 15-40° C.,more preferably 20-30° C., or most preferably 25° C. (+/−10%)) or aconventional/typical elevated temperature. Indeed, in one embodiment,the AF coupling layer 30 may also be deposited using a “heavy” inert gas(for example, xenon (Xe), argon (Ar), and/or krypton (Kr)), at roomtemperature (e.g., 20-30° C.) or an elevated temperature.

In some embodiments, as illustrated in FIG. 4, a pinned layer 15 and apinning layer 14 may be provided between “fixed” region 20 and bottomelectrode 10, with an AF coupling layer 18 magnetically separatingpinned layer 15 and “fixed” region 20. Although “fixed” region 20 isillustrated as a single layer, as explained above, “fixed” region 20 mayinclude a multi-layered structure. Pinned layer 15 may include one ormore of cobalt (Co), iron (Fe), boron (B), and/or alloys thereof.Pinning layer 14 may include an antiferromagnetic alloy such as, forexample, PtMn or IrMn. In general, pinning layer 14 and the pinned layer15 may have any suitable thickness. For example, pinned layer 15 mayhave a thickness of approximately 8 Å to approximately 100 Å, preferablyapproximately 15 Å to approximately 40 Å, and more preferablyapproximately 20 Å to approximately 30 Å. In some embodiments, pinninglayer 14 may have a thickness of approximately 60-300 Å, preferably ofapproximately 100-240 Å, and more preferably of approximately 160-200 Å.As is known to those of ordinary skill in the art, pinning layer 14 andpinned layer 15 may act as a ferromagnetic polarizer where pinning layer14 fixes or pins the direction of the magnetization vector of pinnedlayer 15 and “fixed” region 20.

With renewed reference to FIGS. 1A-1B, a “free” region 60 (or storageregion or layer) may be arranged above “fixed” region 20. Anintermediate layer 50 may be positioned in between “fixed” region 20 and“free” region 60. In some embodiments, the intermediate layer 50 mayinclude dielectric material and may function as a tunnel barrier in anMTJ or MTJ-like structure. In alternative embodiments, the intermediatelayer 50 may include a conductive material, e.g., copper, to form aGMR-type magnetoresistive stack/structure. Intermediate layer 50 may beformed on or above a surface of the “fixed” region 20, and the “free”region 60 may be formed on or above a surface of the intermediate layer50. In general, intermediate layer 50 may be formed on the “fixed”region 20 using any technique now known (e.g., deposition, sputtering,evaporation, etc.) or later developed. In some embodiments, intermediatelayer 50 may include an oxide material, such as, for example, MgO orAlO_(x) (e.g., Al₂O₃), and may be formed by multiple steps of materialdeposition and oxidation. In general, intermediate layer 50 may have anythickness. In some embodiments, the intermediate layer 50 may have athickness of approximately 8.5-14.1 Å, preferably of approximately9.6-13.0 Å, and more preferably of approximately 9.8-12.5 Å.

The “free” region 60 (or “free” magnetic layer) may include one or moreferromagnetic layers. Notwithstanding the specific construction of“free” region 60, “free” region 60 may include a magnetic vector (ormoment) that can be moved or switched by applied magnetic fields,spin-transfer torque from spin-polarized currents, or current-inducedspin-orbit torque. The “free” region 60 may be formed from anyferromagnetic material having two or more stable magnetic states. Aswith conventional magnetoresistive stacks/structures, the direction ofthe magnetization (i.e., the magnetic vector/moment) of the “free”region 60 determines the resistance of magnetoresistive stack/structure100. In practice, for a two-state device, the direction of themagnetization of “free” region 60 is either parallel or anti-parallel tothe magnetization (i.e., the magnetic vector/moment) of the “fixed”region 20, resulting in a low or high resistance representing a “0” bitstate or a “1” bit state, respectively. “free” region 60 may include amagnetic easy axis that defines a natural or default axis ofmagnetization for “free” region 60. When magnetoresistivestack/structure 100 is in a steady state condition (e.g., with nocurrent applied across electrodes 10, 90), the magnetization vector of“free” region 60 will point along its easy axis. In some embodiments,for example those implemented in perpendicular spin-torque devices,“free” region 60 may have a strong perpendicular magnetic anisotropy(PMA) such that its easy axis is perpendicular to the film plane and thetwo stable magnetic states are characterized by a magnetization vectordirected generally toward or away from the intermediate layer 50. It isknown that increasing the PMA of the “free” region 60 may beneficiallyincrease the high temperature data retention capabilities of themagnetoresistive stack/structure 100, e.g., when magnetoresistivestack/structure 100 is implemented as a memory element.

In some aspects, “free” region 60 may include one or more layers ofmagnetic or ferromagnetic material(s). These materials may includealloys of one or more of the ferromagnetic elements nickel, iron, andcobalt. In some embodiments, one or more layers of “free” region 60 alsomay include boron. Additional elements may be added to the alloys toprovide improved magnetic, electrical, or microstructural properties.The one or more layers of “free” region 60 may also include alloys orengineered materials with one or more of, for example, palladium (Pd),platinum (Pt), magnesium (Mg), manganese (Mn), and chromium (Cr). Insome embodiments, similar to “fixed” region 20, “free” region 60 mayalso include one or more SAF or SyF structures. In one or moreembodiments, “fixed” region 20 may include one or more layers ofnon-magnetic materials, such as, for example, ruthenium (Ru), copper(Cu), aluminum (Al), tantalum (Ta), titanium (Ti), niobium (Nb),vanadium (V), zirconium (Zr), iridium (Ir), tungsten (W), molybdenum(Mo), and alloys thereof. In some embodiments, “free” region 60 may beformed of materials that provide a strong PMA. These materials mayinclude ordered L10 alloys (such as, for example, FePt, FePd, CoPt, orFeNiPt), artificial multi-layered structures (such as, Co/Pt, Co/Pd,CoCr/Pt, Co/Au, or Ni/Co), and alloys of CoFeB. In some embodiments,“free” region 60 may include alloys of CoFeB. In general, “free” region60 may have any thickness. In some embodiments, “free” region 60 mayhave a thickness from approximately 7 Å to approximately 40 Å, fromapproximately 20 Å to approximately 30 Å, or from approximately 25 Å toapproximately 28.5 Å.

Although “free” region 60 is illustrated as a single layer in FIGS.1A-1B, this is only exemplary. As alluded to above, some aspects ofmagnetoresistive stack/structure 100 may include a “free” region 60formed of multiple layers stacked one over the other. FIG. 5 illustratesan exemplary multi-layer structure for “free” region 60. Similar toFIGS. 2-4, only certain layers that make up “free” region 60, and onlycertain layers/regions on either side of “free” region 60 (e.g., layers50 and 80) are illustrated in FIG. 5A for the sake of clarity. Asillustrated in FIG. 5A, “free” region 60 may comprise at least twoferromagnetic layers 62, 66 separated by a coupling layer 64. Couplinglayer 64 may provide either ferromagnetic coupling or antiferromagneticcoupling between layers 62, 66.

Coupling layer 64 may include any nonmagnetic material (now known ordeveloped in the future) that can provide coupling (e.g., ferromagneticor antiferromagnetic) between two adjacent ferromagnetic layers 62, 66.In some embodiments, coupling layer 64 may include materials such astantalum (Ta), tungsten (W), molybdenum (Mo), ruthenium (Ru), rhodium(Rh), rhenium (Re), iridium (Ir), chromium (Cr), osmium (Os), andcombinations thereof. Although two ferromagnetic layers 62, 66 areillustrated in FIG. 5, in general, “free” region 60 may have any numberof ferromagnetic layers with respective coupling layers provided betweenadjacent ferromagnetic layers. In general, ferromagnetic layers 62, 66and coupling layer 64 may have any thickness. Typically, the thicknessof coupling layer 64 is chosen to provide strong ferromagnetic orantiferromagnetic coupling between the two ferromagnetic layers 62, 66on either side of the coupling layer 64. In some embodiments,ferromagnetic layers 62 and 66 may have a thickness of approximately3-30 Å, or preferably approximately 6-17 Å, or more preferablyapproximately 8-15 Å. Coupling layer 64 may have a thickness ofapproximately 1-12 Å, or preferably approximately 2-6 Å, or morepreferably approximately 2.5-4 Å. In some embodiments, the thickness ofcoupling layer 64 may be approximately 8 Å or approximately 9 Å. Ingeneral, the coupling layer 64 may comprise a thin layer (comprising,for example, tantalum (Ta), ruthenium (Ru), etc.) positioned betweenferromagnetic layers 62, 66. The thickness of coupling layer 64 may bechosen such that it does not form a continuous layer, which would breakor otherwise inhibit the exchange coupling between adjacent layers 62and 66. Instead, the material of layer 64 may mix with the materials oflayers 62 and 66 to form a uniform layer, or may form a layer that isnot continuous, so that the adjacent ferromagnetic layers 62 and 66 aredirectly exchange coupled to each other and the entire structure acts asa single ferromagnetic “free” layer/region. In some embodiments, thedeposited thickness of coupling layer 64 to achieve this effect is lessthan 3.5 Å, or from 1 Å to 3 Å. Other similar materials that form alloyswith cobalt (Co), iron (Fe), or nickel (Ni) may yield similar results,for example: vanadium (V), zirconium (Zr), titanium (Ti), niobium (Nb),molybdenum (Mo), tungsten (W), hafnium (Hf), manganese (Mn), or chromium(Cr).

With reference now to FIGS. 1A-1B and 5A-5B, embodiments ofmagnetoresistive stack/structure 100 may include an insertion substance80 provided on or above “free” region 60. In embodiments where “free”region 60 includes multiple ferromagnetic layers 62, 66 coupled togetherby a coupling layer 64 (e.g., see FIG. 5), insertion substance 80 may beprovided on the top ferromagnetic layer 66 of “free” region 60. In someembodiments, insertion substance 80 may include a dusting of materialover a surface of “free” region 60. That is, as opposed to a continuousmonolithic layer of material (e.g., a monolayer, which would break theexchange between adjacent layers), insertion substance 80 may include adiscontinuous layer with patches of material deposited on (or otherwiseformed on) the surface of the “free” region 60. For example, in a planview, the insertion substance 80 in FIG. 5A may appear as a patch work,or irregular areas, of material atop the “free” region 60 (which isexposed through gaps between the patches of the insertion substance 80).It should be noted that, although the different insertion substances 80in FIGS. 1 and 5 are illustrated as having generally a similar size(e.g., height), this is only exemplary. In general, insertion substances80 on “free” region 60 may have a various sizes, areas, and geometries.Referring to FIG. 1A-B, providing the insertion substance 80 between the“free” region 60 and a capping layer 86 may result in a highperpendicular magnetic anisotropy (PMA) of the resultingmagnetoresistive stack/structure 100. In some embodiments, when the“free” region 60 includes iron (Fe) and the capping layer 86 includesmagnesium oxide (MgO), the high PMA may be a result of the improvedFe/MgO interface (improved interfacial lattice matching and Fe—Ohybridization at the interface). When an insertion substance 80 isinserted between the “free” region 60 and the capping layer 86, thethickness of insertion substance 80 should be less than one monolayer,so that the material of the capping layer 86 (e.g., magnesium oxide(MgO)) makes physical contact with (i.e., touches) the material of the“free” region 60 (e.g., iron (Fe)) in at least some regions or areas. Insome embodiments, the material of the insertion substance 80 may alloywith a small region of material on the top surface (e.g., top monolayer)of the “free” region 60 and result in a better lattice match with thematerial of the capping layer 86. If the thickness of the insertionsubstance 80 is greater than one monolayer, the material of the cappinglayer 86 (e.g., magnesium oxide (MgO)) may not make physical contactwith the material of the “free” region 60, and thus prevent theformation of a Fe/MgO interface and the resulting high PMA. Therefore,the thickness of the insertion substance 80 may be kept less than onemonolayer.

Insertion substance 80 may include any suitable material, including, butnot limited to, a metal, e.g., a transition metal. In general, anynon-ferromagnetic transition metal element (e.g., a transition metalelement that does not show ferromagnetism at room temperature) may beused to form insertion substance 80. As is known to those of ordinaryskill in the art, transition metal elements comprise elements in the“d-block” of the periodic table, and the lanthanide and actinide serieselements in the “f-block” of the periodic table. More specifically,insertion substance 80 may include, among others, scandium (Sc),titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), copper (Cu),zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo),ruthenium (Ru), rhodium (Rh), palladium (Pd), silver (Ag), cadmium (Cd),indium (In), tin (Sn), antimony (Sb), lanthanum (La), cerium (Ce),praseodymium (Pr), neodymium (Nd), samarium (Sm), europium (Eu), terbium(Tb), dysprosium (Dy), holmium (Ho), erbium (Er), ytterbium (Yb),lutetium (Lu), hafnium (Hf), tantalum (Ta), tungsten (W), rhenium (Re),osmium (Os), iridium (Ir), platinum (Pt), gold (Au), mercury (Hg),thallium (Tl), lead (Pb), and bismuth (Bi). In some embodiments, thethickness of insertion substance 80 may be less than one atomic layer ofthe material selected. In embodiments where insertion substance 80includes iridium (Ir), insertion substance 80 may have a thickness (t)less than approximately 3.33 Å, less than approximately 2 Å, less thanapproximately 1.75 Å, less than approximately 1.66 Å, or fromapproximately 0.1 to approximately 3.33 Å, from approximately 0.4 toapproximately 1.7 Å, or from approximately 0.6 Å to approximately 1.0 Å,or approximately 0.8 Å. In embodiments where insertion substance 80includes chromium (Cr), insertion substance 80 may have a thickness (t)less than approximately 1.44 Å, less than approximately 0.72 Å, or fromapproximately 0.1 Å to approximately 1.44 Å, or from approximately 0.2 Åto approximately 0.9 Å, or from approximately 0.3 Å to approximately 0.7Å, or approximately 0.4 Å.

With renewed reference to FIGS. 1A-1B, magnetoresistive stack/structure100 may further include a capping layer 86 (e.g., a dielectric layer),formed on or above insertion substance 80. Any suitable material may beused to form capping layer 86. For example, capping layer 86 may beformed from any suitable dielectric material, including, but not limitedto, magnesium oxide (MgO) or aluminum oxide (AlO_(x)) ((e.g., Al₂O₃)).Capping layer 86 may have any suitable thickness. In some embodiments,capping layer 86 may have a thickness (t) of approximately 3-14 Å, orpreferably approximately 5-12 Å, or more preferably approximately 6-10Å.

Insertion substance 80 may, among other things, improve the bondingbetween the “free” region 60 and capping layer 86. More specifically,insertion substance 80 may improve the iron-oxygen (Fe—O) bonding at theinterface of “free” region 60 and capping layer 86. The improvediron-oxygen (Fe—O) bonding at the interface of “free” region 60 andcapping layer 86 may result in an increase in PMA without degrading MReffect and/or spin transfer torque. In some embodiments, incorporationof the insertion substance 80 is expected to increase the PMA betweenapproximately 12% and approximately 60%. In some embodiments, anincrease in interfacial anisotropy energy density (K_(s), with typicalunits of erg/cm² in cgs units) of approximately 19% is expected toresult in approximately 35% increase in effective magnetic anisotropyenergy density (Ku^(eff), having units of erg/cc in cgs units), andapproximately 16% increase in anisotropy energy gap (E_(b), usually itis measured in a unit of k_(B)T, like E_(b)/k_(B)T.). It is contemplatedthat the improved iron-oxygen (Fe—O) bonding (and the resulting higherinterfacial PMA) may be the result of a better lattice matching at theinterface of “free” region 60 and capping layer 86. Moreover, it isbelieved that the improved interfacial bonding also may be the result ofminimization (or prevention) of over-oxidation of iron (Fe) at theinterface between “free” region 60 and capping layer 86. Still further,it is believed that the increased PMA results from insertion substance80 optimizing the iron (Fe)-oxygen (O) distance between “free” region 60and capping layer 86.

Although insertion substance 80 may be depicted as a discrete materialwith distinct boundaries in drawings, this may be to clearly illustrateinsertion substance 80 despite its relatively small thickness. In someembodiments, the material of the insertion substance 80 may mix with andform an alloy with the material(s) of “free” region 60 (and/or cappinglayer 86) during downstream processing operations (e.g., annealing,etc.). In such cases, insertion substance 80 may appear as an alloyedregion (e.g., an alloy of the materials of “free” region 60, insertionsubstance 80, and/or capping layer 86) at the interface between thecapping layer 86 and “free” region 60. For example, when the “free”region 60 includes iron (Fe) and the insertion substance 80 includeschromium (Cr), after processing operations, in some embodiments theinsertion substance 80 may alloy with iron (Fe) in a top surface of the“free” region 60 and appear a part of the “free” region 60 with a higherconcentration of chromium (Cr) on the top surface.

Turning now to FIG. 6A, some embodiments of “free” region 60 may furtherinclude another ferromagnetic layer 68 provided on or aboveferromagnetic layer 66. Stated differently, magnetoresistivestack/structure 100 may include a further ferromagnetic layer 68 betweenferromagnetic layer 66 of “free” region 60 and insertion substance 80.In some embodiments, ferromagnetic layer 68 may include iron (Fe) (e.g.,pure iron (Fe) or iron (Fe) in combination with other elements such as,for example, cobalt (Co), nickel (Ni), or boron (B)). For example,ferromagnetic layer 68 may have an iron (Fe) content greater than orequal to 90 at. %, greater than or equal to 95 at. %, greater than orequal to 99 at. %, or greater than or equal to 99.9 at. %. In someembodiments, layer 68 also may include one or more non-magneticmaterials, such as, for example, boron (B), tantalum (Ta), zirconium(Zr), hafnium (Hf), or combinations thereof.

In some embodiments, ferromagnetic layer 68 may function magnetically aspart of “free” region 60. In general, ferromagnetic layer 68 may haveany thickness and may be formed as a continuous layer or a discontinuouslayer (e.g., patches) over ferromagnetic layer 66. In some embodiments,ferromagnetic layer 68 may have a sub-atomic thickness. For example,ferromagnetic layer 68 may have a thickness from approximately 1.5 Å toapproximately 7 Å, less than approximately 5 Å, or less thanapproximately 3 Å. Similar to that described above with reference toinsertion substance 80, in some embodiments, after high temperatureprocessing operations (e.g., annealing), ferromagnetic layer 68 mayalloy with the materials of one or both of “free” region 60 andinsertion substance 80. In such embodiments, ferromagnetic layer 68 mayappear as a region of increased concentration of the material(s) oflayer 68 (e.g., iron (Fe)) at the interface between “free” region 60 andinsertion substance 80. As shown in FIGS. 1A-B, electrode 90 may beformed on or above capping layer 86 to complete the magnetoresistivestack/structure 100. As illustrated in FIG. 6B, in some embodiments, thecoupling layer 64 between ferromagnetic layers 62 and 66 may be replacedwith an insertion layer 64′ (e.g., of tantalum (Ta), molybdenum (Mo),etc. having a thickness, for example, of approximately 3 Å). In someembodiments, insertion layer 64′ may alloy with the adjacentferromagnetic layers 62 and 66 during downstream processing operations(e.g., annealing) allowing the formation of a larger “free” region oflayer 60.

Turning now to FIG. 7, there is depicted one exemplary embodiment ofmagnetoresistive stack/structure 100, having the exemplary “fixed”region 20 of FIG. 3 and the “free” region 60 of FIG. 6A. As those withordinary skill in the art will recognize, magnetoresistivestack/structure 100 may have any suitable layers or configurations. Forexample, “fixed” region or layer 20 may have any structure orconfiguration, including those illustrated in any of FIGS. 1A-4.Similarly, “free” region 60 may have any structure, including thoseillustrated in any of FIGS. 1A-B and 5-7. In addition to the exemplarystacks/structure described herein, many other stacks/structures may beused in connection with the magnetoresistive stack/structure 100 and/orinsertion substance 80 described herein. For example, U.S. Pat. Nos.8,686,484; 9,136,464; and 9,419,208, each assigned to the assignee ofthe current application and incorporated by reference in its entiretyherein, disclose several exemplary stacks/structures of magnetoresistivestack/structure 100 and methods of making such magnetoresistivestacks/structures 100. Specifically, “fixed” region 20 and “free” region60 may have any of the structures/configurations disclosed in thesereferences.

In some embodiments, magnetoresistive stack/structure 100 may includeone or more additional layers, such as, e.g., spacer layer 88. As shownin FIG. 7, spacer layer 88 may be formed between electrode 90 andcapping layer 86. In general, capping layer 86 may have any thicknessand may be formed of any suitable material (e.g., MgO, Al₂O₃, MgAlO_(x),or other suitable dielectric materials). In some embodiments, spacerlayer 88 may be formed of a non ferromagnetic material, such as, e.g.,ruthenium (Ru) or tantalum (Ta) or an alloy of ruthenium (Ru) ortantalum (Ta). In some embodiments, spacer layer 88 may include cobalt(Co), iron (Fe), boron (B), or an alloy thereof (e.g., CoFeB). In someembodiments, spacer layer 88 may include one or more materials orelements also included in capping layer 86. For example, both cappinglayer 86 and spacer layer 88 may include oxygen (O). In addition, spacerlayer 88 may include one or more materials or elements not present incapping layer 86. For example, capping layer 86 may be formed of MgO,and spacer layer 88 may be formed of CoFeB. In some embodiments, thethickness of the spacer layer 88 may be approximately 5-50 Å, orpreferably approximately 10-35 Å, or more preferably approximately 22-28Å.

As previously explained, although the individual layers of FIG. 7 (andother figures) are illustrated as distinct layers with sharp welldefined boundaries, typically, the materials of two adjacent layers atan interface (between the layers) may diffuse into each other, andpresent an interfacial region of an alloy or a combination of thematerials of the two individual layers. Further, while all of the layersillustrated in FIG. 7 (and other figures) may be present anddistinguishable immediately after formation of the individual layer, insome embodiments, it may be difficult to distinguish some of the layers(e.g., layers of sub-atomic thickness, such as, for example, layers 30,64, 68, 80, 86, 88) as a separate layer in a finished product. Instead,these layers may appear as an interfacial region having a higherconcentration of an element or material present in an adjacent layer.

As explained above, FIGS. 1 and 7 depict exemplary embodiments of amagnetoresistive stack/structure 100 having an insertion substance 80(e.g., a metal), according to the present disclosure. The exemplarymagnetoresistive stacks/structures 100 include a “fixed” region 20 and a“free” region 60 separated by an intermediate layer 50 (e.g., adielectric layer) to form an MTJ-like device. As explained previously,an MTJ has a low resistance state and a high resistance state, and theratio of the change in resistance between its high and low resistancestates is commonly referred to as the magnetoresistance (“MR”) ofmagnetoresistive stack/structure 100. Providing an insertion substance80 (e.g., a metal such as a transition metal including, but not limitedto, iridium (Ir) or chromium (Cr)) on or over “free” region 60 (e.g.,above the MTJ formed by “fixed” region 20, “free” region 60, andintermediate layer 50) may increase the interfacial PMA at the interfaceof “free” region 60 and capping layer 86, without affecting the MR orthe MR ratio of the MTJ.

In another embodiment of the present disclosure, aspects describedherein may be used in connection with magnetoresistive stack/structure200 depicted in FIG. 8. As alluded to above, magnetoresistivestack/structure 200 may include a magnetoresistive memorystack/structure or a magnetoresistive sensor/transducer stack/structure.When implemented as an MTJ or MTJ-like memory device, magnetoresistivestack/structure 200 may be referred to as a dual spin filter structureor a double spin filter structure. In some aspects, the dual spin filterstructure of magnetoresistive stack/structure 200 may require lesscurrent to switch a magnetization direction a “free” region 60.

Magnetoresistive stack/structure 200 may include one or more regions orlayers described in connection with magnetoresistive stack/structure100. For example, magnetoresistive stack/structure 200 also may includea bottom electrode 10, a seed region 12, a “fixed” region 20, a firstintermediate layer 50 (e.g., made of a dielectric material), a “free”region 60, insertion substance 80, capping layer 86 (and/or a spacerlayer 88, see FIG. 7), and top electrode 90. One or more of bottomelectrode 10, a seed region 12, a “fixed” region 20, a firstintermediate layer 50 (e.g., made of a dielectric material), a “free”region 60, insertion substance 80, capping layer 86, and electrode 90 ofmagnetoresistive stack/structure 200 may include any aspect (e.g.,material or thickness) described above in connection withmagnetoresistive stack/structure 100. Those of ordinary skill in the artwill understand that the intermediate layer 50 may include a conductor,e.g., copper, to form a GMR-type device.

As compared to magnetoresistive stack/structure 100, magnetoresistivestack/structure 200 may include a second intermediate layer 150 formedon or above insertion substance 80. In general, intermediate layer 150may include the same material or a different material as intermediatelayer 50. In some embodiments, both intermediate layer 50 andintermediate layer 150 may include a dielectric material (such as, forexample, MgO) and may function as a tunnel barrier. However, this is nota limitation, in some embodiments, intermediate layer 50 andintermediate layer 150 may include different dielectric materials. Forexample, intermediate layer 50 may include MgO and intermediate layer150 may include AlO_(x) (e.g., Al₂O₃). In some embodiments, intermediatelayer 150 also may be similar in thickness to intermediate layer 50. Inother embodiments, intermediate layer 150 may have a thickness that islarger or smaller than the thickness of intermediate layer 50. In someembodiments, intermediate layer 150 may have a thickness ofapproximately 3-14 Å, preferably of approximately 5-12 Å, and morepreferably of approximately 6-10 Å.

Magnetoresistive stack/structure 200 may include another “fixed” regionor layer 120 formed on or above intermediate layer 150. Capping layer 86and electrode 90 then may be formed on or above “fixed” region or layer120. In some embodiments, as explained previously, a spacer layer 88 maybe provided above the capping layer 86. Although fixed region or layer120 is illustrated as a single layer, “fixed” region or layer 120 mayinclude a multi-layered structure, e.g., as described in connection withone of FIGS. 2-4 above.

“fixed” region 20, intermediate layer 50, and “free” region 60 maytogether form a first MTJ (e.g., MTJ₁) having a first MR (e.g., MR₁) anda first RA (e.g., RA₁), and “fixed” region or layer 120, intermediatelayer 150, and “free” region 60 may together form a second MTJ (e.g.,MTJ₂) having a second MR (e.g., MR₂) and a second RA (e.g., RA₂). Asthose of ordinary skill in the art will recognize, the overall MR ofmagnetoresistive stack/structure 200 may be maximized when one MTJ(e.g., MTJ₁) dominates the resistance change by having a much largerresistance change than the other MTJ (e.g., MTJ₂) when the “free” region60 changes state. This is usually accomplished by having a dominant MTJ,which includes both a larger MR and a larger RA than the other MTJ. Oneof the two MTJs may be made a dominant MTJ by suitable selection of thematerials and/or thicknesses of the layers in the two MTJs. Sincemethods of making a dominant MTJ is known to those of ordinary skill inthe art, they are not described herein. For example, U.S. Pat. No.9,419,208, which is incorporated by reference herein, disclosesexemplary methods of a making one of the two MTJs of a dual-spin filtermemory element a dominant MTJ.

With specific reference to magnetoresistive stack/structure 200, MTJ₁(i.e., the MTJ formed by “fixed” region 20, intermediate layer 50, and“free” region 60) may be a dominant MTJ as compared to MTJ₂ (i.e., theMTJ formed by “fixed” region or layer 120, intermediate layer 150, andthe “free” region 60). The overall MR of magnetoresistivestack/structure 200 may increase when the MR of MTJ₁ increases and theMR of MTJ₂ decreases. Insertion substance 80, formed at the interfacebetween the “free” region 60 and the intermediate layer 150 (of MTJ₂)may increase the PMA at the interface and decrease the MR of MTJ₂.However, since insertion substance 80 is provided above MTJ₁, insertionsubstance 80 may have no effect (or minimal effect) on the MR of MTJ₁.Thus, addition of insertion substance 80 increases the overall MR ofmagnetoresistive stack/structure 200 by reducing MR₂ as compared to MR₁.

As alluded to above, magnetoresistive stack/structure 100, 200 may beimplemented in a sensor architecture or a memory architecture (amongother architectures). For example, in a memory configuration,magnetoresistive stack/structure 100, 200 may be electrically connectedto an access transistor and configured to couple or connect to variousconductors, which may carry one or more control signals, as shown inFIG. 9.

Magnetoresistive stack/structure 100, 200 of the current disclosure maybe used in any suitable application, including, e.g., in a memoryconfiguration. In such instances, magnetoresistive stack/structure 100,200 may be formed as integrated circuits comprising a discrete memorydevice (e.g., as shown in FIG. 10A) or an embedded memory device havinga logic therein (e.g., as shown in FIG. 10B), each including MRAM,which, in one embodiment is representative of one or more arrays of MRAMhaving a plurality of magnetoresistive stacks/structures, according tocertain aspects of certain embodiments disclosed herein.

Exemplary methods of fabricating selected embodiments of the disclosedmagnetoresistive stack/structure 100, 200 will now be described. Itshould be appreciated that the described methods are merely exemplary.In some embodiments, the methods may include a number of additional oralternative steps, and in some embodiments, one or more of the describedsteps may be omitted. Any described step may be omitted or modified, orother steps added, as long as the intended functionality of thefabricated magnetoresistive stack/structure remains substantiallyunaltered. Further, although a certain order is described or implied inthe described methods, in general, the steps of the described methodsneed not be performed in the illustrated and described order. Further,the described methods may be incorporated into a more comprehensiveprocedure or process having additional functionality not describedherein.

FIG. 11 depicts a flow chart of an exemplary method 300 of fabricatingmagnetoresistive stack/structure 100. In the discussion below, referencewill be made to both FIGS. 1A-B and 11. A first electrode (e.g., bottomelectrode 10) may be first formed by any suitable process, including,e.g., deposition (step 310). In some embodiments, electrode 10 may beformed on a surface of a substrate that defines a plane. A “fixed”region or layer 20 then may be formed on an exposed surface of electrode10 (step 320). That is, the “fixed” region or layer 20 may be formed onthe surface of electrode 10 that is opposite the surface that interfaceswith the surface of the substrate. An intermediate layer 50 then may beformed on an exposed surface of the “fixed” region or layer 20 (step330), and a “free” region or layer 60 may be formed on an exposedsurface of the intermediate layer 50 (step 340). Next, an insertionsubstance 80 (e.g., including a metal, such as, e.g., a transitionmetal, including chromium or iridium) then may be formed on an exposedsurface of the “free” region or layer 60 (step 350), and a capping layer86 may be formed atop (i.e., on an exposed surface of) the insertionsubstance 80 (step 360). A second electrode 90 then may be formed on asurface of the capping layer 86 (step 370). In some embodiments, thesecond electrode 90 may be eliminated and a bit line may be providedabove the stack. It should be noted that, in embodiments where the“fixed” layer or region 20 and/or the “free” region or layer 60 includesa multi-layer configuration (e.g., as shown in FIGS. 2-3 and 5-7), steps320 and 340 may include any suitable substeps (not shown) for formingthe multiple layers that makeup “fixed” layer or region 20 and “free”region or layer 60.

FIG. 12 illustrates a flow chart of an exemplary method 400 of makingmagnetoresistive stack/structure 200. In method 400, steps 310 through350 may first be carried out as described with reference to FIG. 11.After insertion substance 80 is formed (e.g., step 350 of FIG. 11), asecond intermediate layer 150 may be formed over (e.g., on an exposedsurface of) insertion substance 80 (step 410) (see, e.g., FIGS. 8 and12). Second intermediate layer 150 may be formed such that the MR andthe RA associated with intermediate layer 150 is less than the MR and RAassociated with intermediate layer 50 (formed in step 330 of FIG. 11).Next, a second “fixed” region or layer 120 may be formed on an exposedsurface of second intermediate layer 150 (step 420). A capping layer 86then may be formed on an exposed surface of the second “fixed” region orlayer 120, and a second (e.g., top) electrode 90 may be formed on anexposed surface of the capping layer 86. As explained with reference toFIG. 11, in some embodiments, the second electrode 90 may be eliminatedand a bit line may be provided above the stack.

In some embodiments, magnetoresistive stack/structure 100, 200 may befabricated by forming each succeeding layer directly on a surface of thelayer/region below. For instance, with reference to FIG. 7, in someembodiments, seed region 12 may be formed directly on a surface (e.g.,top surface in FIG. 7) of electrode 10, and ferromagnetic layer 22 maybe formed directly on a top surface of seed layer 12, and so forth. Anysuitable method may be used to form the different regions or layers.Since suitable integrated circuit fabrication techniques (e.g.,deposition, sputtering, evaporation, plating, etc.) that may be used toform the different layers are known to those of ordinary skill in theart, they are not described here in great detail. In some embodiments,forming some of the layers may involve thin-film deposition processes,including, but not limited to, physical vapor deposition techniques suchas ion beam sputtering and magnetron sputtering. And, forming thininsulating layers, such as the tunnel barrier layers, may involvephysical vapor deposition from an oxide target, such as byradio-frequency (RF) sputtering, or by deposition of a thin metallicfilm followed by an oxidation step, such as oxygen plasma oxidation,oxygen radical oxidation, or natural oxidation by exposure to alow-pressure oxygen environment.

In some embodiments, formation of some or all of the layers ofmagnetoresistive stack/structure 200 may also involve known processingsteps such as, for example, selective deposition, photolithographyprocessing, etching, etc., in accordance with any of the variousconventional techniques known in the semiconductor industry. In someembodiments, during deposition of the disclosed “fixed” and “free”regions or layers, a magnetic field may be provided to set a preferredeasy magnetic axis of the region/layer (e.g., via induced anisotropy).Similarly, a strong magnetic field applied during the post-depositionhigh-temperature anneal step may be used to induce a preferred easy axisand a preferred pinning direction for any antiferromagnetically pinnedmaterials.

Although various embodiments of the present disclosure have beenillustrated and described in detail, it will be readily apparent tothose skilled in the art that various modifications may be made withoutdeparting from the present disclosure or from the scope of the appendedclaims.

In some embodiments, a disclosed magnetoresistive device may comprise afixed magnetic region, a free magnetic region, and an intermediate layerdisposed in between the fixed magnetic region and the free magneticregion. The device may also include an insertion layer disposed on orabove the free magnetic region. The insertion layer may include one ofchromium or iridium, and the insertion layer may include a thicknessless than 2 Å. In some embodiments, the disclosed device may include oneor more of the following features: the intermediate layer may include adielectric material; the intermediate layer may include a conductivematerial; the fixed magnetic region may include a multilayer syntheticantiferromagnetic structure; the thickness of the insertion layer may be0.2 Å-0.7 Å; the thickness of the insertion layer may be less than 0.8Å; the device may further include a capping layer disposed on or abovethe insertion layer, wherein the insertion layer is positioned betweenthe capping layer and the free layer; the device may further include asecond fixed region disposed on or above the insertion layer, whereinthe insertion layer is positioned between the second fixed region andthe free region.

In some embodiments, a method of manufacturing a magnetoresistive stackincludes depositing a fixed magnetic region on an electricallyconductive material, depositing a free magnetic region, and depositingan intermediate layer in between the fixed magnetic region and the freemagnetic region. The disclosed method may also include depositing aninsertion layer on or above the free magnetic region. The insertionlayer may include one of chromium and iridium and may include athickness less than 2 Å. Various embodiments of the disclosed method mayalso include one or more of the following aspects: the method mayfurther include depositing a dielectric layer on or above the insertionlayer, and depositing a second fixed region on or above the dielectriclayer; the intermediate layer may include a dielectric material; theintermediate layer may include a conductive material; and the fixedmagnetic region may include a multilayer synthetic antiferromagneticstructure.

What is claimed is:
 1. A magnetoresistive device comprising: a fixed magnetic region positioned on or over a first electrically conductive region; an intermediate layer positioned on or over the fixed magnetic region; a free magnetic region positioned on or over the intermediate layer; and a metal insertion substance positioned in contact with the free magnetic region, wherein the metal insertion substance includes one or more transition metal elements.
 2. The magnetoresistive device of claim 1, further comprising: a seed region disposed between the first electrically conductive region and the fixed magnetic region, wherein the seed region is in contact with both the first electrically conductive region and the fixed magnetic region; and a second electrically conductive region positioned above the metal insertion substance.
 3. The magnetoresistive device of claim 1, wherein the one or more transition metal elements include at least one of chromium (Cr) or iridium (Ir).
 4. The magnetoresistive device of claim 1, wherein the metal insertion substance may have a thickness less than or equal to approximately 3.33 Å.
 5. The magnetoresistive device of claim 1, further comprising: a capping layer disposed on or over the metal insertion substance, and wherein the capping layer has a thickness of approximately 3 Å to approximately 14 Å.
 6. The magnetoresistive device of claim 5, wherein the “free” magnetic region comprises: a first magnetic layer including iron (Fe), cobalt (Co), and/or boron (B); a coupling layer formed on or over the first magnetic layer, wherein the coupling layer includes tantalum (Ta), tungsten (W), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), rhenium (Re), iridium (Ir), chromium (Cr), osmium (Os), or combinations thereof; and a second magnetic layer formed on or over the coupling layer, wherein the second magnetic layer includes iron (Fe), cobalt (Co), and/or boron (B).
 7. The magnetoresistive device of claim 1, wherein the metal insertion substance is provided adjacent to an iron-rich region of the free magnetic region.
 8. The magnetoresistive device of claim 1, further comprising an electrically conductive line positioned adjacent to the free magnetic region.
 9. The magnetoresistive device of claim 1, further comprising an electrically conductive line positioned in contact with the free magnetic region.
 10. A magnetoresistive device comprising: a first fixed magnetic region; a first intermediate layer formed adjacent to the first fixed magnetic region; a free magnetic region formed adjacent to the intermediate layer; a metal insertion layer formed adjacent to the free magnetic region, wherein the metal insertion layer includes one or more transition metal elements configured to be non-magnetic in an elemental state at 15° C.-40° C.; a second intermediate layer formed adjacent the metal insertion substance; and a second fixed magnetic region formed adjacent the second intermediate layer.
 11. The magnetoresistive device of claim 10, wherein the magnetoresistive device further comprises one or more of: a seed region disposed adjacent to the first fixed magnetic region on a side opposite to the first intermediate layer; or a capping region positioned adjacent to the second fixed magnetic region on a side opposite to the second intermediate layer.
 12. The magnetoresistive device of claim 10, wherein the one or more transition metal elements include chromium (Cr) and iridium (Ir).
 13. The magnetoresistive device of claim 10, wherein the one or more transition metal elements includes chromium (Cr), and wherein the metal insertion layer includes a thickness less than or equal to 1 Å.
 14. The magnetoresistive device of claim 10, wherein the one or more transition metal elements includes iridium (Ir), and wherein the metal insertion layer includes a thickness less than or equal to 2 Å.
 15. The magnetoresistive device of claim 10, wherein the metal insertion layer is positioned adjacent to an iron-rich region of the free magnetic region.
 16. A magnetoresistive device comprising: a first fixed magnetic region positioned on or over a first electrically conductive region; a first intermediate layer positioned on or over the first fixed magnetic region; a free magnetic region positioned on or over the first intermediate layer, the free magnetic region comprising: a first magnetic layer including iron (Fe), cobalt (Co), and/or boron (B); a coupling layer formed on or over the first magnetic layer, wherein the coupling layer includes tantalum (Ta), tungsten (W), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), rhenium (Re), iridium (Ir), chromium (Cr), osmium (Os), or combinations thereof; and a second magnetic layer formed on or over the coupling layer, wherein the second magnetic layer includes iron (Fe), cobalt (Co), and/or boron (B); a metal insertion substance provided adjacent to the free magnetic region, wherein the metal insertion substance includes one or more of chromium (Cr) and iridium (Ir); a second intermediate layer positioned adjacent to the metal insertion substance; and a second fixed magnetic region positioned adjacent to the second intermediate layer.
 17. The magnetoresistive device of claim 16, further comprising an electrical conductor in contact with the free magnetic region.
 18. The magnetoresistive device of claim 16, wherein the metal insertion substance includes a chromium (Cr) layer having a thickness less than or equal to 1 Å.
 19. The magnetoresistive device of claim 16, wherein the metal insertion substance includes an iridium (Ir) layer having a thickness less than or equal to 2 Å.
 20. The magnetoresistive device of claim 16, wherein the metal insertion substance is provided adjacent an iron-rich region of the free magnetic region. 